(1) Field of the Invention
The present invention relates to a variable frequency signal generator.
(2) Description of the Related Art
Previously, to perform injected signal measurements to verify system performances required multiple bulky pieces of expensive test equipment. This equipment often would not easily provide the pulse to pulse parameter agility with the accuracy and stability offered by the invention described herein.
The precision microwave/millimeter wave modulated signal source of the invention is a relatively low cost, compact, highly accurate and stable signal source covering the 2 to 40 Gigahertz (GHz) frequency range. The pulse width and amplitude level of the output signal can be changed on every pulse in the signal pulse train. Pulse width range is 5 nanoseconds to 1 millisecond. Pulse repetition intervals can be changed between each pulse set with usable range from 10 nanoseconds to 100 milliseconds. Interval parameters can be adjusted with 1 nanosecond resolutions with stabilities of +/xe2x88x92200 picoseconds. The highly accurate and versatile selection of signal parameters, along with its compact size, makes this design useful as an embedded built in test signal source. This built in signal source can be used for verification of system performance for many electronic warfare systems.
The invention outputs precision microwave/millimeter wave modulated signals to various. frequency bands. The source of radio frequency (RF) is a miniature oscillator that injects a low frequency at high power. This output is fed into a step recovery diode that generates many combed output frequencies. This spectrum is then modulated by a programmed high precision pulse repetition interval (PRI) signal coming from a circuit board containing pulse characteristics as small as 1 nanosecond (s) pulsewidth. One frequency picket at a time is filtered by a yttrium iron garnet (YIG) filter and appropriate attenuation is set by a digitally variable attenuator to yield the desired precision microwave/millimeter modulated signals.